Chapter 2. Program OrganizationGFK-2950C February 2018 272.3.2 Timed InterruptsA block can be configured to execute on a specified time interval with an initial delay (if specified)applied on a STOP Mode to RUN Mode transition of the CPU.To configure a timed interrupt block, specify the following parameters in the scheduling propertiesfor the block:Time Base The smallest unit of time that you can specify for Interval and Delay. The time base can be 1.0second, 0.10 second, or 0.01 second, or 0.001 second.Interval Specifies how frequently the block executes in multiples of the time base.Delay (Optional) Specifies an additional delay for the first execution of the block in multiples of thetime base.The first execution of a Timed Interrupt block will occur at((delay * time base) + (interval * time base)) after the CPU is placed in RUN Mode.2.3.3 I/O InterruptsA block can be triggered by an interrupt input from certain hardware modules. For example, on the32-Circuit 24 Vdc Input Module (IC697MDL650), the first input can be configured to generate aninterrupt on either the rising or falling edge of the input signal. If the interrupt is enabled in themodule configuration, that input can serve as a trigger to cause the execution of a block.To configure an I/O interrupt, specify a trigger in the scheduling properties for the block. The triggermust be a global variable in %I, %AI or %AQ memory, or an I/O variable. (An I/O variable is a form ofsymbolic variable that is mapped to a module I/O point in hardware configuration.)PACSystems modules that can trigger user interrupt logic always send the interrupt to the CPUwhen configured to do so. If the CPU is in STOP mode when it receives the interrupt, it does not runthe user interrupt block. The CPU does not run the user interrupt block when it transitions fromSTOP Mode to RUN Mode.2.3.4 Module InterruptsA block can be triggered by an interrupt from a module that supports I/O interrupts if the Interruptparameter is enabled in the module’s hardware configuration.To configure a module interrupt, specify the module by rack/slot/interrupt ID as the Trigger in thescheduling properties for the block.
